Arc furnace having consumable and non-consumable electrodes and method

ABSTRACT

An arc furnace having a first, non-consumable electrode in the form of a rotatable, cooled wheel within an evacuated housing and a second consumable electrode shiftably mounted within the housing for movement toward the first electrode as the latter rotates and after an arc has been established between the two electrodes. A crucible carried by the housing is positioned below the arc to receive molten material from the consumable electrode as the latter melts due to the heat of the arc. In one form of the invention, the mounting shaft for the first electrode extends upwardly and away from the second electrode. In another form of the invention, the shaft extends downwardly and away from the consumable electrode. In a third embodiment, means are provided to direct a gas under pressure to the arc to atomize the molten material before it is collected in the crucible therebelow.

United States Patent [191 Schlienger June 18, 1974 ARC FURNACE HAVING CONSUMABLE AND NON-CONSUMABLE ELECTRODES AND METHOD [76] Inventor: Max P. Schlienger, l9 Rollingwood Dr., San Rafael, Calif, 94901 [22] Filed: Sept. 4, 1973 [21] Appl. No.: 393,871

[52] U.S. Cl 13/9, l3/18, 13/31, 13/34 [SI] Int. Cl. H05b 7/06 [58] Field of Search 13/9, 18, 34, 31

[56] References Cited UNITED STATES PATENTS 3,420,939 l/l969 Schlienger 13/I8 3,65'l,238 3/1972 Schlienger 13/9 Primary Examiner-Roy N. Envall, Jr.

[57] ABSTRACT An arc furnace having a first, non-consumable electrode in the fomi of a rotatable, cooled wheel within an evacuated housing and a second consumable electrode shiftably mounted within the housing for movement toward the first electrode as the latter rotates and after an arc has been established between the two electrodes. A crucible carried by the housing is positioned below the arc to receive molten material from the consumable electrode as the latter melts due to the heat of the arc. In one form of the invention, the mounting shaft for the first electrode extends upwardly and away from the second electrode. In another form of the invention, the shaft extends downwardly and away from the consumable electrode. In a third embodiment, means are provided to direct a gas under pressure to the arc to atomize the molten material before it is collected in the crucible therebelow.

18 Claims, 5 Drawing Figures VACUUM SYSTEM ARC FURNACE HAVING CONSUMABLE AND NONCONSUMABLE ELECTRODES AND METHOD method for maintaining a first electrode in a relatively cool condition to keepit from melting as a second consumable electrode is being melted by an arc established between the electrodes.

BACKGROUND OF THE INVENTION In the use of arc furnaces, a need often arises for melting certain refractory and other special metals containing a high percentage of volatiles which are difficult to melt by processes such as the electron beam melting process. It is useful also to drip melt such materials to purify or maintain the purity thereof as well as to permit the same to change into a powdery consistency. Moreover, by drip melting such materials into a crucible used with the electron beam process, the materials can readily be melted again and refined by the application of electron beam heating.

All of the foregoing requires an efficient arc furnace system which provides for drip melting of a consumable electrode formed of the above materials. However, such an electrode must be used with another nonconsumable electrode to sustain an electric arc there between to cause melting of the first electrode. The non-consumable electrode must be kept from melting; otherwise, the desired melt will be contaminated and the arc will not be sustained.

SUMMARY OF THE INVENTION The present invention is directed to an improved arc furnace and method which is capable of drip melting a consumable electrode of the above materials in an efficient manner to purify or maintain the purity of the materials notwithstanding the need for another electrode which itself must be kept from melting under the influence of the electric are established between the two electrodes. To this end, the present invention utilizes a non-consumable electrode in the form of a rotatable wheel in conjunction with theconsumable electrode. The advantage of using the wheel as an electrode is that the wheel can be cooled as it is rotated to eliminate erosion of the non-consumable electrode yet permit an arc to be sustained between the electrodes as the consumable electrode melts. Thus, a fixed non-consumable electrode is not needed so that a relatively high electric field can be utilized to keep the temperature of the arc at a high value and sufficiently high to cause the melting of the consumable electrode to be in the form of drops or droplets.

The arc furnace of this invention is constructed so that the consumable electrode can move progressively toward the electrode wheel, thereby allowing the molten metal to continue to drip toward and to be collected in a crucible below the are as the length of the consumable electrode becomes increasingly shorter. The melt is done without melting the surface of the electrode wheel because the wheel is not only rotated but it is also cooled by a coolant flowing therethrough. Thus, no one part of the electrode wheel is continuously subjected to the heat of the arc, and such heat is distributed over the electrode wheel while being dissipated due to the coolant flow therethrough.

The electrode wheel can be mounted for rotation about an inclined axis with a portion of the electrode wheel overlying the consumable electrode tip. In the alternative, the electrode wheel can be mounted so that a portion of it underlies the consumable electrode. In either case, the consumable electrode tip is melted while the electrode wheel is rotatable about an inclined axis. In either case, the molten material drips toward and into a crucible beneath the arc.

Another aspect of the invention is the use of a fluid nozzle with the above two electrodes to direct 'a fluid, such as a suitable gas, into the region the arc established between the electrodes to atomize the molten metal asit gravitates from the region of the arc. Thus, the atomized particles form a powder which can be further processed, such as being cooled by gravitating, for instance on a rotatable, cooled table therebelow.

The primary object of this invention is to provide an improved arc furnace and method of melting a consumable electrode of refractory or other special metal wherein a shiftable, consumable electrode is movable progressively toward a rotatable, cooled, wheel-like electrode after an arc has been established between the electrodes to cause the metal to melt and to drip into a crucible below the region of the arc.

Another object of this invention is to provide an arc furnace of the type described wherein the wheel-like electrode is mounted for rotation about an axis which is inclined with respect to the consumable electrode to assure that the molten melt will drip into the crucible therebelow yet a coolant can be directed through the wheel-like electrode to dissipate the heat energy absorbed thereby to prevent it from eroding as the consumable electrode melts.

A further object of this invention is to provide an arc furnace of the aforesaid character wherein a fluid can be directed into the arc to atomize the molten metal formed thereby before such molten metal gravitates to a receptacle therebelow to thereby permit the atomized metal to be in the form of a powder.

Other objects of this inventionwill become apparent as the following specification progresses, reference being had to the accompanying drawings for illustrations of several embodiments of the arc furnace of the invention.

IN THE DRAWINGS FIG. 1 is a schematic view of a first embodiment of the arc furnace with the wheel-like electrode rotatable about an inclined axis and overlying the tip of the consumable electrode;

FIG. 2 is an enlarged, fragmentary, cross-sectional view of the wheel-like electrode;

FIG. 3 is a cross-sectional view taken along line 33 of FIG. 2;

FIG. 4 is a fragmentary view similar to FIG. I but showing the use of a fluid nozzle adjacent to the electrodes for directing and atomizing gas toward the region of the arc formed therebetween; and

FIG. 5 is a fragmentary view similar to FIG. 1 but showing another embodiment of the arc furnace with the wheel-like electrode at a different angle with respect to the consumable electrode.

A first embodiment of the system of this invention is broadly denoted by the numeral 10 and includes a housing 12 shown schematically in FIG. 1. The housing has a chamber 14 in which a rotary wheel-like eIectrode 16 is disposed above a crucible 18 having an open top Communicating with chamber 14. A consumable electrode 20 has a tip 22 adjacent to and spaced from a generally flat, inclined face 23 of electrode 16 to permit an electric are 24 to be struck between the wheel and tip 22 to melt the tip and to cause drops 26 of mo]- ten metal to gravitate from, tip 22 into the open top of crucible'l8 as shown in FIG. 1. A vacuum system 28 is provided to evacuate chamber 14 to maintain the purity of materials comprising electrode 20 as the materials drip in the form of drops 26. A valve 30 controls the evacuation of chamber 14. Means 32 is provided to drive consumable electrode 20 to the left when viewing FIG. 1 as the electrode progressively becomes shorter in length due to the melting thereof by are 24. Housing l2has a first sidewall 34 extending upwardly from a bottom wall 36 through which crucible 18 extends. A bearing 38 carried by sidewall 34 rotatably mounts an inclined shaft 40 and isolates same from housing 12 coupled at one end thereof to wheel 16, The shaft is tubular as shown in FIG. 2 for apurpose described hereinafter. Also, the shaft extends through and is rotatable relative to a fluid distribution member 42 toadmit fluid to and to permit removal of fluid from the shaft. To this end, a fluid inlet pipe 44 and a fluid outlet pipe 46 are coupled to member 42 and communicate with shaft 40 in a manner to be described.

Shaft 40 also makes electrical contact with an electrical terminal, such as a fixed contact 48 electrically coupled by lead 50 to the positive side of a source 52 of electrical power, the negative side of source 52 being electrically coupled by a lead 54 to a metallic sleeve 56 whichserves as a holder for electrode 20 and which extends outwardly from bearing 58 mounted in a second sidewall 60 in housing 12. Bearing 58 allows sleeve 56 to move progressively into thehousing as the length of electrode 20 progressively decreases. Means for rotating shaft includes a drive motor 62 .having a drive shaft 64 and gear means 66 interconnecting drive shaft 64 and wheel shaft 40. Thus, upon actuation of motor 62, wheel 16*is caused to rotate about'its central axis to minimize the time in which any one portion of the wheel is used to sustain'arc 24 for each revolution of the wheel. t

Wheel 16 is of the type shown in FIGS. 2 and 3 and includes a circular, flat plate 68 having an annular flange 70 which is coupled by screws 72 to an annular flange 74 on the: adjacent end of shaft 40.

Shaft 40 is tubular to present a fluid passage 76 in surrounding relationship to an inner, fixed tube 78 terminating'at an end face 80 on an end wall 81 of shaft 40. A bearing 82'carried in a central opening in end wall 81 mounts shaft 40 for rotation with respect to tube 78. Also, tube 78 communicates by way of an annular passage 83 with a plurality of fluid passages 84 in end face 80, the passages 84 being tangential to the end of tube '78 as shown in FIG. 3. Thus, coolant flowing in the direction of arrow 86 through tube 78 will enter passages 84and flow outwardly along the same and then will be returned to passage 76 by way of a number of angularly disposed, relatively short passages 88 extending through the junction between flange 74 and end wall8l of shaft 40 as shown in FIG. 2. Arrows 90 indicate the entry of the coolant into passage 88 for re turn to the source of coolant by way of pipe 46. Pipe 44 will be in fluid communication with tube 78 to supply the coolant thereto.

Crucible 18 can be of any suitable type, such as the withdrawal type utilizing a piston 92 on a stem 94 coupled to a power device 96 for withdrawing stem 94 and moving the piston downwardly. Piston 92 serves as the movable bottom of the crucible and can move downwardly as the mass 98 in the crucible increases in volume. Electrode 20 is supported at one end by sleeve 56 in bearing 58 and at its other end by a roller 100 of a base 102 on a support surface 104 of housing 12. Means 32 for advancingelectrode 20 includes a fluid piston and cylinder assembly 106 attached in any suitable manner to housing 12 and provided with a piston rod 108 parallel to sleeve 56 and coupled thereto by a link 1l0.'

. through the wheel, the wheel is caused to rotate bythe actuation of motor 62. Then, voltage is applied to wheel 16 and electrode 20 and the electrode is moved sufficiently close to the wheel to cause the arc to be struck therebetween. When are 24 is struck, piston 92 of crucible 18 will be nearer the top of the crucible so as to collect the initial drops 26 caused by the melting of electrode 20 due to the heat of are 24.

Asthe electrode 24'continues to melt, drops 26 are continually collected in the crucible and piston 92 is progressively moved downwardly as the volume of mass 98 increases. Also, electrode 20 progresses toward wheel 16 under the influence of fluid piston in cylinder assembly 106 as the length of the electrode becomes shorter due to themelting thereof. Tip 22 of electrode 20 remains spaced from face 23 of wheel electrode 16 to sustain the arc therebetween. Since chamber 14 is evacuated, no impurities react with drops 26 as they gravitate toward and into the crucible. If desirable, additional heat can be added at the crucible to enableproducing a homogeneous ingot. However, the melted drops will stick together and form an electrode which could be remelted or converted to powder for powder metallurgical applications.

During the melting of electrode 20, coolant continually flows through wheel 16 in a manner described above with respect to FIGS. 2 and 3. The diameter of I the wheel is sufficiently large and the'cooling capacity is sufficiently great to enable melting of electrode 20 without melting the'surface of wheel 16. This system permits the melting of materials containing high percentages of volatile materials which are difficult to melt by processes such as the. electron beam melting process. It also enables dropping the metal into an electron beam crucible where it can be further melted and de-. fined by the application of electron beam heating.

Another embodiment of the arc furnace system is shown in FIG. 4 and is denoted by the numeral 110. System 110 is substantially the same in all respects as system 10 of FIG. l except that wheel electrode 116 thereof is inclined at the angle shown in FIG. 4 namely with the flat circular face 117 of the wheel being inclined and facing upwardly and toward the consumable electrode 120 rather than downwardly as in the case of wheel 16 of system 10. Wheel 116 has the same construction as that shown in FIGS. 2 and 3 and is mounted by a bearing 1 18 in sidewall 134 of housing 12 for rotation relative thereto. The operation of system 110 is substantially the same as that described above with respect to system 10.

FIG. 5 illustrates the use of a gas jet 130 with the electrode wheel 16 of system to atomize the molten material to form a powder from electrode 20. After the arc is struck, the gas jet atomizes the droplets and causes them to form a powdery mass 132 which gravitates intoa tube 134. Powder particles from tube 134 can bb metered therefrom and deposited on a rotating table 136 having a horizontal upper surface 138 below tube 134. Table 136 can be cooled in substantially the same way as wheel 116 such as by a coolant flowing through fluid entry and exit pipes and a fluid distributor member "(not shown) similar in all respects to pipes 44 and 46 and member 42 of system 10. Such a distributor member will be coupled to the rotatable shaft or pedestal 138 of table 136.

What is claimed is:

1. An arc furnace comprising: a housing adapted to be evacuated and provided with a lower extremity; a crucible coupled with the housing near the lower ex tremity and provided with an open top; a wheel defining a first non-consumable electrode; means mounting the wheel within the housing for rotation with respect thereto; means coupled with the wheel for rotating the same relative to the housing; means coupled with the wheel for cooling the same as it rotates relative to the housing; a second consumable electrode; means coupled with the housing for mounting the second electrode therein for movement toward the wheel with one end of the second electrode being in proximity to the wheel and in alignment with and above said open top of the crucible; means coupled with the electrodes for connecting the same to a source of electrical power to cause an electrical field to be established therebetween, withthe intensity of the electrical field being sufficient to initiate and to sustain an arc in a region between the electrodes, whereby the second electrode will be melted and the material melted therefrom will gravitate into said crucible; means adjacent to said second electrode mounting means for moving the second electrode toward said wheel as the second electrode is melted in said are; and means coupled with the wheel for rotating the same with respect to the housing.

2. An arc furnace as set forth in claim 1, wherein the wheel mounting means includes a shaft inclined upwardly and away from the second electrode, and means mounting the shaft on the housing for rotation relative thereto.

3. An arc furnace as set forth in claim 1, wherein the wheel mounting means includes a shaft inclined downwardly and away from the second electrode, and means mounting the shaft on the housing for rotation relative thereto.

4. An arc furnace as set forth in claim 1, wherein is included a fluid nozzle carried by the housing and adapted to be coupled to a source of a fluid under pressure, the nozzle being adjacent to said region to direct a fluid under pressure thereinto after the arc has been established across the same to atomize the metal melted from the second' electrode.

5. An arc furnace as set forth in claim 4, wherein is provided a cooling platform below said region to receive and cool the atomized metal gravitating from said region.

6. An arc furnace as set forth in claim 1, wherein said second electrode mounting means comprises an electrode holder, said housing having a sidewall, and including a bearing coupled with said sidewall for mounting the holder for movement through the sidewall said moving means including a fluid piston and cylinder assembly coupled with the holder for shifting the same along said path.

7. An arc furnace as set forth in claim 6, wherein said mounting means includes a roller in said housing in spaced relationship to said bearing to provide a second support for the second electrode.

8. An arc furnace as set forth in claim 1, wherein said wheel mounting means includes a first, tubular shaft having said wheel rigid thereto, bearing means coupled to said first shaft for mounting the same on said housing, there being a second, tubular shaft mounted within and spaced from the first shaft, said cooling means including a coolant distributor having a coolant inlet coupled to and communicating with one of the tubes and a coolant outlet coupled to and communicating with the other tube, there being fluid passage means in heat exchange relationship to said wheel for placing said tubes in communication with each other.

9. An arc furnace as set forth in claim 8, wherein said first shaft has an end wall provided with a central opening therethrough, said second shaft extending into said opening, said end wall having a number of fluid passages formed therein, said fluid passages being in fluid communication with said shafts.

10. An arc furnace as set forth in claim 9, wherein the fluid passages are tangential to the second shaft.

11. An arc furnace comprising: a housing having a lower portion and a pair of opposed sides; means coupled with the housing for evacuating the interior thereof; means coupled with the housing near one side thereof for mounting a first, consumable electrode therewithin for movement along a predetermined path relative thereto; a second electrode in the form of a wheel; means adjacent to the opposite side of the housing for rotatably mounting the wheel in said housing with an outer face of the wheel adjacent to and spaced from one end of the first electrode; an open top crucible carried by the lower portion of the housing in alignment with the space between the first and second electrodes to receive molten material gravitating from said first electrode when an electric arc established between the electrodes melts the first electrode; means coupled with the electrodes for coupling the same to a source of electrical power to cause an arc-forming electric field to be established between the electrodes; means coupled with the first electrode for shifting the same toward the second electrode; means coupled with the second electrode for rotating the same relative to the housing; and means coupled with the second electrode for cooling the same as the latter rotates relative to the housing and when an arc has been established between the first and second electrodes.

metal from the consumable electrode to gravitate in drops from the region of the arc; rotating the other electrode about an inclined axis through said face as the arc is sustained between the electrodes; directing a coolant through the other electrode asthe latter is rotated; progressively moving a first of said electrodes toward the second electrode as the length of the con- 15. A method as set forth in claim 12, wherein the face of the other electrode faces upwardly and toward the tip of the consumable electrode.

16. A method as set forth in claim 12, wherein is included the step of directing a gas under pressure into the region of the arc to atomize the drops formed by the melting of the consumable electrode to thereby cause the drops to bein the form of a powder.

17. A method as set forth in claim 16, wherein is included the step of cooling the powder after the latter has gravitated from the region of the are.

18. A method as set forth in claim 12, wherein is included the step of evacuating the space in which the electrodes are disposed.

I 'UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 5, 5 I Dated June 18, 197R Max P. Schlienger Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

v On the Title page the following should be added:

[7i Assignee: Sohinger, Inc. San Rafael, Calif.

- Signed sealed this 17th day of December 19 74.]

(SEAL) Attest:

' McCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer Commissioner of Patents v UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 3, 5 Dated June 18, 197 L Inventor(s) Max Chllenger It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the Title page the following should be added:

-- [7i Assignee: Schinger, Inc. San Rafael, Calif.

Signed ahd sealed this 17th day of December 1974.1

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 

1. An arc furNace comprising: a housing adapted to be evacuated and provided with a lower extremity; a crucible coupled with the housing near the lower extremity and provided with an open top; a wheel defining a first non-consumable electrode; means mounting the wheel within the housing for rotation with respect thereto; means coupled with the wheel for rotating the same relative to the housing; means coupled with the wheel for cooling the same as it rotates relative to the housing; a second consumable electrode; means coupled with the housing for mounting the second electrode therein for movement toward the wheel with one end of the second electrode being in proximity to the wheel and in alignment with and above said open top of the crucible; means coupled with the electrodes for connecting the same to a source of electrical power to cause an electrical field to be established therebetween, with the intensity of the electrical field being sufficient to initiate and to sustain an arc in a region between the electrodes, whereby the second electrode will be melted and the material melted therefrom will gravitate into said crucible; means adjacent to said second electrode mounting means for moving the second electrode toward said wheel as the second electrode is melted in said arc; and means coupled with the wheel for rotating the same with respect to the housing.
 2. An arc furnace as set forth in claim 1, wherein the wheel mounting means includes a shaft inclined upwardly and away from the second electrode, and means mounting the shaft on the housing for rotation relative thereto.
 3. An arc furnace as set forth in claim 1, wherein the wheel mounting means includes a shaft inclined downwardly and away from the second electrode, and means mounting the shaft on the housing for rotation relative thereto.
 4. An arc furnace as set forth in claim 1, wherein is included a fluid nozzle carried by the housing and adapted to be coupled to a source of a fluid under pressure, the nozzle being adjacent to said region to direct a fluid under pressure thereinto after the arc has been established across the same to atomize the metal melted from the second electrode.
 5. An arc furnace as set forth in claim 4, wherein is provided a cooling platform below said region to receive and cool the atomized metal gravitating from said region.
 6. An arc furnace as set forth in claim 1, wherein said second electrode mounting means comprises an electrode holder, said housing having a sidewall, and including a bearing coupled with said sidewall for mounting the holder for movement through the sidewall said moving means including a fluid piston and cylinder assembly coupled with the holder for shifting the same along said path.
 7. An arc furnace as set forth in claim 6, wherein said mounting means includes a roller in said housing in spaced relationship to said bearing to provide a second support for the second electrode.
 8. An arc furnace as set forth in claim 1, wherein said wheel mounting means includes a first, tubular shaft having said wheel rigid thereto, bearing means coupled to said first shaft for mounting the same on said housing, there being a second, tubular shaft mounted within and spaced from the first shaft, said cooling means including a coolant distributor having a coolant inlet coupled to and communicating with one of the tubes and a coolant outlet coupled to and communicating with the other tube, there being fluid passage means in heat exchange relationship to said wheel for placing said tubes in communication with each other.
 9. An arc furnace as set forth in claim 8, wherein said first shaft has an end wall provided with a central opening therethrough, said second shaft extending into said opening, said end wall having a number of fluid passages formed therein, said fluid passages being in fluid communication with said shafts.
 10. An arc furnace as set forth in claim 9, wherein the fluid passages are tangential to the second shaft.
 11. An arc furnace comprising: a housing having a lower portion and a pair of opposed sides; means coupled with the housing for evacuating the interior thereof; means coupled with the housing near one side thereof for mounting a first, consumable electrode therewithin for movement along a predetermined path relative thereto; a second electrode in the form of a wheel; means adjacent to the opposite side of the housing for rotatably mounting the wheel in said housing with an outer face of the wheel adjacent to and spaced from one end of the first electrode; an open top crucible carried by the lower portion of the housing in alignment with the space between the first and second electrodes to receive molten material gravitating from said first electrode when an electric arc established between the electrodes melts the first electrode; means coupled with the electrodes for coupling the same to a source of electrical power to cause an arc-forming electric field to be established between the electrodes; means coupled with the first electrode for shifting the same toward the second electrode; means coupled with the second electrode for rotating the same relative to the housing; and means coupled with the second electrode for cooling the same as the latter rotates relative to the housing and when an arc has been established between the first and second electrodes.
 12. A method of melting a consumable electrode comprising: mounting the electrode in a generally horizontal position adjacent to and spaced from another electrode having an inclinded face; striking and sustaining an electric arc between the electrodes to cause the metal from the consumable electrode to gravitate in drops from the region of the arc; rotating the other electrode about an inclined axis through said face as the arc is sustained between the electrodes; directing a coolant through the other electrode as the latter is rotated; progressively moving a first of said electrodes toward the second electrode as the length of the consumable electrode decreases; and collecting the drops of metal at a location below said region.
 13. A method as set forth in claim 12 wherein, the step of directing said coolant through the second electrode includes urging the coolant in heat exchange relationship to said face of the other electrode.
 14. A method as set forth in claim 12, wherein the face of the other electrode faces upwardly and toward the tip of the consumable electrode.
 15. A method as set forth in claim 12, wherein the face of the other electrode faces upwardly and toward the tip of the consumable electrode.
 16. A method as set forth in claim 12, wherein is included the step of directing a gas under pressure into the region of the arc to atomize the drops formed by the melting of the consumable electrode to thereby cause the drops to be in the form of a powder.
 17. A method as set forth in claim 16, wherein is included the step of cooling the powder after the latter has gravitated from the region of the arc.
 18. A method as set forth in claim 12, wherein is included the step of evacuating the space in which the electrodes are disposed. 